The optical communication path network (to be also referred to as optical path network) that supports current backbone networks and metro networks are mainly formed by optical communication apparatuses (that may be referred to as node apparatuses) such as wavelength multiplexing transmission apparatuses and optical add drop apparatuses (ROADM: Reconfigurable add drop multiplexer and the like), transmission routes such as optical fibers connecting them, and optical communication paths such as wavelength for connecting the optical communication apparatuses via the transmission routes. Especially, research and development are getting attention for a transparent-type optical communication path network that forms an optical communication path between an optical communication apparatus of a transmission end and an optical communication apparatus of a receiving end without recover and relay processing for optical signals in relay sections.
In the following, an optical communication method and apparatus in the conventional transparent type optical communication path network are described in the following.
FIG. 1 shows an example of a conventional ring-type optical communication path network (refer to non-patent document 1, for example). The optical communication path network includes optical communication apparatuses 1-8. As shown in FIG. 2, each of the optical communication apparatuses 1-8 mainly includes a transmission function unit 11 including a transmission function of a main signal, a receiving function unit 12 including a receiving function, a route exchange function unit 13 including a wavelength multiplexing-demultiplexing unit and an optical switch, and a control unit 16 configured to control the transmission function unit 11, the receiving function unit 12 and the route switch function unit 13. Also, optical amplifiers 14 and 15 are provided according to the level of the optical signal.
In addition, in the optical communication apparatus at the input side (transmission end) of the optical communication path, the transmission function unit 11 converts an electrical signal transmitted from a client into an optical signal and outputs the optical signal, then, the route exchange function unit 13 switches a destination of the output optical communication path to a designated destination. Also, at the optical communication apparatus in the output side (receiving end) of the optical communication path, the route exchange function unit 13 switches the destination of the optical communication path to the receiving function unit 12, so that the receiving function unit 12 converts the optical signal into the electrical signal. The optical communication apparatus in the relay side switches between routes for each optical communication path.
According to the above-mentioned optical communication method, processes for optical signals are reduced in the optical communication apparatuses in the relay section. Thus, it is expected to realize economization, space-saving, and power saving for the optical communication path network